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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup sync
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file
  35.  * @brief   Semaphores.
  36.  */
  37.  
  38. #include <synch/semaphore.h>
  39. #include <synch/waitq.h>
  40. #include <synch/spinlock.h>
  41. #include <synch/synch.h>
  42. #include <arch/asm.h>
  43. #include <arch.h>
  44.  
  45. /** Initialize semaphore
  46.  *
  47.  * Initialize semaphore.
  48.  *
  49.  * @param s Semaphore.
  50.  * @param val Maximal number of threads allowed to enter critical section.
  51.  */
  52. void semaphore_initialize(semaphore_t *s, int val)
  53. {
  54.     ipl_t ipl;
  55.    
  56.     waitq_initialize(&s->wq);
  57.    
  58.     ipl = interrupts_disable();
  59.  
  60.     spinlock_lock(&s->wq.lock);
  61.     s->wq.missed_wakeups = val;
  62.     spinlock_unlock(&s->wq.lock);
  63.  
  64.     interrupts_restore(ipl);
  65. }
  66.  
  67. /** Semaphore down
  68.  *
  69.  * Semaphore down.
  70.  * Conditional mode and mode with timeout can be requested.
  71.  *
  72.  * @param s Semaphore.
  73.  * @param usec Timeout in microseconds.
  74.  * @param flags Select mode of operation.
  75.  *
  76.  * For exact description of possible combinations of
  77.  * usec and flags, see comment for waitq_sleep_timeout().
  78.  *
  79.  * @return See comment for waitq_sleep_timeout().
  80.  */
  81. int _semaphore_down_timeout(semaphore_t *s, __u32 usec, int flags)
  82. {
  83.     return waitq_sleep_timeout(&s->wq, usec, flags);
  84. }
  85.  
  86. /** Semaphore up
  87.  *
  88.  * Semaphore up.
  89.  *
  90.  * @param s Semaphore.
  91.  */
  92. void semaphore_up(semaphore_t *s)
  93. {
  94.     waitq_wakeup(&s->wq, WAKEUP_FIRST);
  95. }
  96.  
  97. /** @}
  98.  */
  99.